How to create a shared calendar (yandex mail + outlook\thunderbird)?

Question

Yandex

At the moment, the following scheme is used:
A separate account has been created in the domain Yandex mail purely for the calendar, which we connect to users with outlook\thunderbrd via CalDavSynchronizer. As a result, when a user creates an event for a certain time and invites several participants to a meeting, a user who is not invited to this meeting will see that the office is currently busy and will be able to create a new event for another time. In general, the scheme is working, but several disadvantages gradually begin to annoy:
1. For some reason, notifications about the created meeting do not always come. No matter what checkboxes I put in the settings, this bug still appears.
2. The organizer of the meetings is not visible, although there is a checkmark about this (
3. Attached files are not visible (only for the organizer)
4. Participants who are not invited to this event can go to an already created event and change it (that is, there is no elementary separation by rights)
How to solve this problem?
Personally, I still see only the installation of Exchange with the transfer of all mailboxes to it (and at the same time raising AD, as I understand it). Which is very expensive in terms of labor costs, for a long time. And then, it's not clear whether this will work in Mozilla Thunderbird?... Perhaps there are some other options? Or maybe somehow you can connect Exchange without transferring mailboxes in order to use only the functionality of the common calendar \ appointments \ events, etc.?
Colleagues, please share your experience. Thanks in advance to everyone who responds.

Answer 1

Why exactly Yandex? If you connect a calendar to MS Outlook, then it would be logical to create a calendar on Outlook.com, where exchange synchronization will be out of the box. With mozilla, everything is really complicated.
You can also automatically pull events from Google calendar to Microsoft calendar (Outlook.com) via Microsoft Flow.

Answer 2

Solutions:

• CalDAV Synchronizer: free, open source
  
• OpenProtocols Connector: Free for personal use, business - $25/year or less
  
• EVO Collaborator for Outlook: almost the same as CalDAV Synchronizer, but paid, 28 euros
  

The name is googling